The present invention relates to the field of ultrasonic atomizing inhalers, and in particular to an improved oscillating construction for such an ultrasonic atomizing inhaler which improves on the prior art.
There are various types of ultrasonic atomizing inhalers; one of these typically has a horn construction for vibrating at an ultrasonic frequency and for atomizing liquid supplied thereto, and the atomized liquid drifts away from said horn construction and enters into the mouth and/or the nose of a user. Such an ultrasonic atomizing inhaler is typically used for the inhalation of liquid medicine, and for humidification of the larynx of the user.
The horn construction of a typical such ultrasonic atomizing inhaler is shown in FIG. 1a of the accompanying drawings in side view, and in FIG. 1b in an end on view. In this inhaler, the cone shaped horn construction e serves for concentrating ultrasound waves produced at its larger end a by the vibration of an ultrasonic oscillating element c which is driven by an oscillation circuit g, into its smaller end b, so as to vibrate an oscillating plate d integrally formed at its said smaller end b. A supply of liquid such as medicine is held in a storage bottle (not shown), and is picked up therefrom by a wick construction or absorptive bar f and is delivered little by little to the oscillating plate d by capillary action, whence it is atomized into the air by the vibrations of said oscillating plate d, to drift into the mouth and the throat and lungs of a user. And the horn construction b is held in place by a flange h which is connected to a main body (not shown) of the inhaler.
In such a conventional ultrasonic atomizing inhaler, the oscillation member such as the plate d is typically a circular plate or disk, and proper atomization is possible only when the oscillation frequency produced by the oscillation circuit g and the resonance frequency of the oscillation plate d are well matched, so that said plate d becomes excited. But, when the supply of liquid from the absorptive bar f or the load condition has changed, as for example when a more viscous liquid is being used for atomization than before, the resonance frequency of the oscillation plate d with the load of liquid thereon accordingly changes, whereby the atomization action is weakened. Also, by droplets which have not been atomized adhering to the atomization surface of the oscillation plate d and thereby causing overload, the power consumption for driving the oscillation circuit g can become increased, and the durability of the battery is thereby undesirably reduced. When the quantitative control of the liquid supply is not proper, droplets tend to build up on the atomization surface of the oscillation plate d, thereby causing over supply of liquid, and because the liquid is not properly atomized by the power of the device the droplets have to be removed by hand, which is a great inconvenience and is also wasteful of possibly expensive liquid such as costly medication. Also, in the worst case, these accumulated droplets could dribble down out of the atomizer, which would be very messy. Therefore, in order to accomplish proper atomization, it is necessary to properly control the liquid supply, but since the liquid supply unit (not shown) is often removed away from the atomization plate d of the horn e for supply and replenishing of liquid, the engagement between the liquid supply unit and the atomization plate d of the horn e tends to change every time they are put together, whereby it has been difficult to satisfy the above mentioned conditions. Accordingly, unsatisfactory atomization action has sometimes occurred with the prior art.
Another problem that has tended to occur with ultrasonic atomizing inhalers of this sort has related to particle size. The optimum particle size for inhalation of medication into the larynx varies according to the type of the medication and according to the exact point in the respiratory tract to which the medication is to be applied and to the symptoms of the patient, and in particular application of medication to the deep part of the trachea requires quite a different particle size for the atomized medication from that required by application to the shallow part of the larynx. Accordingly, it is desirable for an ultrasonic atomizing inhaler to be able to operate to atomize medication into particles of differing particle size. However, since the oscillation plate of the horn of a conventional ultrasonic atomizer is circular, it can have only one basic resonance frequency, and accordingly only can satisfactorily perform atomization at one frequency and at one particle size, with respect to a particular type of medication. Therefore, in order to change the average particle size of the atomized particles, it is necessary to prepare a plurality of ultrasonic atomizers (or, at least, horn assemblies) having different resonance frequencies.
Another problem that has tended to occur with ultrasonic atomizing inhalers of this sort has related to support of the horn assembly. Conventionally, the horn assembly has been supported within the main body of the inhaler in one of two ways. Either a flange has been integrally formed around the circumferential direction of the horn main body at a longitudinal position therealong corresponding to a node of the longitudinal oscillations thereof, said flange being coupled to said main body of said inhaler by its outer periphery being fitted into a groove therein (this structure is suggested in FIG. 1); or, alternatively, at said longitudinal position along the horn main body corresponding to a node of the longitudinal oscillations thereof, a circumferential groove has been formed, and the inner periphery of an annular retaining member has been fitted into this circumferential groove, the outer periphery of said annular retaining member being fitted into a groove in said main body of said inhaler.
However, the mass and the dimension of the horn of a typical such ultrasonic atomizing inhaler, and particularly of the horn of such an inhaler intended for home use, have become so small that, when an oscillation of frequency from 100 kHz to 300 kHz is to be produced in such a horn, although it may be possible in theory to compute an oscillation nodal point to be used as a support point, if a flange or groove is to be provided at said point as mentioned above, the dimensional precision of such a flange or groove must be very high. Accordingly, the machining process is caused to be very difficult, and accordingly the cost is raised. This problem has been a serious obstacle to providing an ultrasonic inhaler which is economical enough for home use. And, even with the utmost diligence, it is not practicable to support the horn assembly at a true nodal point at which the amplitude of the longitudinal oscillation is zero, and accordingly some elasticity in the support construction has been required. Furthermore, when such a flange or groove is formed in an extremely small horn for supporting it, effects from oscillation modes other than the longitudinal oscillation mode may be produced, and the atomization efficiency may be impaired.
Another type of problem that occurs with ultrasonic atomizing inhalers of this sort has related to electrical connection to the horn assembly. Typical schemes for connection to a conical type horn assembly and to a stepped type horn assembly are shown in FIGS. 12 and 13 of the appended drawings in side view: for the conical type horn assembly of FIG. 12, two lead wires 9a and 9b are soldered at their one ends to appropriate points on a circuit base board 8, and at their other ends, respectively, to an end surface of the ultrasonic oscillation element 3, and to a side wall 1 of the conical horn assembly. And, in a similar way, in the step type horn assembly of FIG. 13, two lead wires 20a and 20b are soldered at their one ends to appropriate points on a circuit base board 19, and at their other ends, respectively, to an end surface of the ultrasonic oscillation element 3, and to a side wall 11 of the step type horn assembly. But the problem arises with such a connection construction that, since the horn assembly is very small with the ceramic ultrasonic oscillation element thereon typically having a diameter of from 10 to 20 millimeters in diameter, the work of fixing such lead wires to the horn assembly, especially by soldering, has been very troublesome and prone to error.
Another type of problem that occurs with ultrasonic atomizing inhalers of this sort has related to heating up of the horn assembly. The temperature of the horn assembly rises sharply during the action of the ultrasonic oscillation element, and may attain a level close to 100.degree. C. Therefore, such heating up could cause an averse effect in the adhesion portion between the horn assembly and the ultrasonic oscillation element, in the worst case causing peeling off of the ultrasonic oscillation element and damaging the oscillation capability of the horn assembly. In order to avoid this inconvenience, it might be considered desirable to provide a heat dissipation mechanism for the horn assembly, but, in a conventional ultrasonic atomizing inhaler of the sort described above, since the horn assembly has been supported on the main body case by a flange or by a groove, it has not been possible to provide a heat dissipation mechanism which can be guaranteed not to disrupt the oscillation of the horn assembly.